Ponències/Comunicacions de congressoshttp://hdl.handle.net/2117/3998
Fri, 01 Dec 2017 22:27:05 GMT2017-12-01T22:27:05ZGravitomagnetic separation of bipolar charged martian dusthttp://hdl.handle.net/2117/110090
Gravitomagnetic separation of bipolar charged martian dust
Arias Montenegro, Francisco Javier
The possible role of magnetic anomalies on Mars in gravitational enhancement of separation of charged dust is considered. It is known that charges become spatially separated by differential transport and gravitational sedimentation because the charge polarity of particles od dust depends on the particle size - where smaller particles are negatively charged and larger particles are positively charged; thus smaller and predominantly negative charged particles populate higher regions of dust devils, and larger, positively charged particles fall to the ground. This study shows that gravitational separation could be enhanced by the presence of magnetic anomalies on Mars owing to the generation of a type of magnetobarrier that prevents gravitational settling of charged dust particles beyond a certain size threshold.
Tue, 07 Nov 2017 14:15:24 GMThttp://hdl.handle.net/2117/1100902017-11-07T14:15:24ZArias Montenegro, Francisco JavierThe possible role of magnetic anomalies on Mars in gravitational enhancement of separation of charged dust is considered. It is known that charges become spatially separated by differential transport and gravitational sedimentation because the charge polarity of particles od dust depends on the particle size - where smaller particles are negatively charged and larger particles are positively charged; thus smaller and predominantly negative charged particles populate higher regions of dust devils, and larger, positively charged particles fall to the ground. This study shows that gravitational separation could be enhanced by the presence of magnetic anomalies on Mars owing to the generation of a type of magnetobarrier that prevents gravitational settling of charged dust particles beyond a certain size threshold.The response of an elastic membrane to an external flow as drag enhancement techniquehttp://hdl.handle.net/2117/108380
The response of an elastic membrane to an external flow as drag enhancement technique
Arias Montenegro, Francisco Javier; Heras Jiménez, Salvador Augusto de las
The response of an elastic membrane to an external flow and its significance with regard to aerodynamic drag enhancement technique is discussed. It is shown that because the response of an elastic membrane to an external flow and the development of Kelvin-Helmholtz instabilities due to the relative motion between the atmosphere and the spacecraft, the flapping of the membrane will translate in a ulsating pressure onto the walls which added to the skin drag friction will increase the apparent drag force exerted by the surrounding media, i.e, a drag enhancement technique. Utilizing a simplified linear and inviscid stability analysis an estimate for the response of the membrane as well as the drag enhancement was obtained. The technique could be particularly interesting for descent spacecraft vehicles in planets with reduced atmosphere as Mars.
Thu, 05 Oct 2017 13:59:49 GMThttp://hdl.handle.net/2117/1083802017-10-05T13:59:49ZArias Montenegro, Francisco JavierHeras Jiménez, Salvador Augusto de lasThe response of an elastic membrane to an external flow and its significance with regard to aerodynamic drag enhancement technique is discussed. It is shown that because the response of an elastic membrane to an external flow and the development of Kelvin-Helmholtz instabilities due to the relative motion between the atmosphere and the spacecraft, the flapping of the membrane will translate in a ulsating pressure onto the walls which added to the skin drag friction will increase the apparent drag force exerted by the surrounding media, i.e, a drag enhancement technique. Utilizing a simplified linear and inviscid stability analysis an estimate for the response of the membrane as well as the drag enhancement was obtained. The technique could be particularly interesting for descent spacecraft vehicles in planets with reduced atmosphere as Mars.The flow over a high-viscosity fluid layer as a drag enhancement techniquehttp://hdl.handle.net/2117/108379
The flow over a high-viscosity fluid layer as a drag enhancement technique
Arias Montenegro, Francisco Javier; Heras Jiménez, Salvador Augusto de las
It is well known that hydrodynamic drag reduction can be obtained by locally surround-ing an immersed solid boundary with another low viscosity-fluid resulting in a lubricating effect. In aerodynamics propulsion, this principle has been used in the so called super-cavitation, in which the viscous drag resistance acting on a, say, torpedo or submarine is substantially reduced by enclosing the body in a low-viscosity gas bubble. In this paper we are exploring the same idea but in an opposite direction, namely: we want to know if creating a high-viscosity fluid layer or film can result in an anti-lubricating effect in which the viscous drag resistance is substantially increased, i.e., a drag enhancement technique. The main motivation behind this idea is in application to the Red planet for landing large payloads as for example in future human missions with payloads several factors larger than an unmanned spacecraft and where the thin atmosphere of Mars sharply reduce the aerobraking capabilities. Utilizing a simplified turbulent layer model the theoretical justification of this rather intuitive idea is outlined. Some preliminary computational fluid dynamics calculations were performed which encourage further research.
Thu, 05 Oct 2017 13:10:57 GMThttp://hdl.handle.net/2117/1083792017-10-05T13:10:57ZArias Montenegro, Francisco JavierHeras Jiménez, Salvador Augusto de lasIt is well known that hydrodynamic drag reduction can be obtained by locally surround-ing an immersed solid boundary with another low viscosity-fluid resulting in a lubricating effect. In aerodynamics propulsion, this principle has been used in the so called super-cavitation, in which the viscous drag resistance acting on a, say, torpedo or submarine is substantially reduced by enclosing the body in a low-viscosity gas bubble. In this paper we are exploring the same idea but in an opposite direction, namely: we want to know if creating a high-viscosity fluid layer or film can result in an anti-lubricating effect in which the viscous drag resistance is substantially increased, i.e., a drag enhancement technique. The main motivation behind this idea is in application to the Red planet for landing large payloads as for example in future human missions with payloads several factors larger than an unmanned spacecraft and where the thin atmosphere of Mars sharply reduce the aerobraking capabilities. Utilizing a simplified turbulent layer model the theoretical justification of this rather intuitive idea is outlined. Some preliminary computational fluid dynamics calculations were performed which encourage further research.Parametric analysis of active flow control using steady suction and steady blowinghttp://hdl.handle.net/2117/107917
Parametric analysis of active flow control using steady suction and steady blowing
Prakash, Bhanu; Mellibovsky Elstein, Fernando; Bergadà Granyó, Josep Maria
Active Flow Control is implemented over NACA 2412 airfoil using Steady Suctionand Steady Blowing techniques. The pre-stall angle of attack (AOA) 12 0 is studied at a high Reynolds number (Re chord ) of 3.1*10 6 for two-dimensional, incompressible and steady flow conditions. A wide range of parametric value set is considered for Slot location (l s ), Velocity magnitude ratio (U j /U 0 ), slot width (w) and angle of perturbation (ß) using both steady suction and steady blowing independently. The numerical modeling is done using the corresponding solver in OpenFOAM, an open source CFD framework. The turbulence modeling is done using Reynolds Averaged Navier Stokes (RANS) equations, specifically k-k l -¿ model implementation in OpenFOAM. The impact of the parametric set on aerodynamic coefficients, lift (C l ) and drag( C d ), and flow separation is illustrated. Along with, the relevant boundary layer physics are explained.
Fri, 22 Sep 2017 12:38:36 GMThttp://hdl.handle.net/2117/1079172017-09-22T12:38:36ZPrakash, BhanuMellibovsky Elstein, FernandoBergadà Granyó, Josep MariaActive Flow Control is implemented over NACA 2412 airfoil using Steady Suctionand Steady Blowing techniques. The pre-stall angle of attack (AOA) 12 0 is studied at a high Reynolds number (Re chord ) of 3.1*10 6 for two-dimensional, incompressible and steady flow conditions. A wide range of parametric value set is considered for Slot location (l s ), Velocity magnitude ratio (U j /U 0 ), slot width (w) and angle of perturbation (ß) using both steady suction and steady blowing independently. The numerical modeling is done using the corresponding solver in OpenFOAM, an open source CFD framework. The turbulence modeling is done using Reynolds Averaged Navier Stokes (RANS) equations, specifically k-k l -¿ model implementation in OpenFOAM. The impact of the parametric set on aerodynamic coefficients, lift (C l ) and drag( C d ), and flow separation is illustrated. Along with, the relevant boundary layer physics are explained.NACA 2412 performance modification via using AFChttp://hdl.handle.net/2117/107734
NACA 2412 performance modification via using AFC
Summ, Thorsten; Prakash, Bhanu; Bergadà Granyó, Josep Maria; Wierschem, Andreas; Mellibovsky Elstein, Fernando
The NACA 2412 profile was numerically studied via employing 2D-DNS and implementing Active Flow Control (AFC), the Reynolds number considered was 6757, being the angle of attack of 8º. Initially, the basic flow without implementing AFC was considered, the point in which the boundary layer separates as well as the y+ value along the profile length were evaluated. A single groove location, just before the separation point, was considered, periodic forcing was employed to both modify the location of the separation point and change the separation area where vortices are present. This was undertaken resulting in a reduction of the drag coefficient while increasing the lift. Via studying a set of frequencies and amplitudes linked with the AFC periodic actuation, it was obtained the optimum set of parameters to minimize the drag while maximizing the lift.
Mon, 18 Sep 2017 12:48:14 GMThttp://hdl.handle.net/2117/1077342017-09-18T12:48:14ZSumm, ThorstenPrakash, BhanuBergadà Granyó, Josep MariaWierschem, AndreasMellibovsky Elstein, FernandoThe NACA 2412 profile was numerically studied via employing 2D-DNS and implementing Active Flow Control (AFC), the Reynolds number considered was 6757, being the angle of attack of 8º. Initially, the basic flow without implementing AFC was considered, the point in which the boundary layer separates as well as the y+ value along the profile length were evaluated. A single groove location, just before the separation point, was considered, periodic forcing was employed to both modify the location of the separation point and change the separation area where vortices are present. This was undertaken resulting in a reduction of the drag coefficient while increasing the lift. Via studying a set of frequencies and amplitudes linked with the AFC periodic actuation, it was obtained the optimum set of parameters to minimize the drag while maximizing the lift.Fluidic actuator performance variation via internal dimensions modificationshttp://hdl.handle.net/2117/107732
Fluidic actuator performance variation via internal dimensions modifications
Baghaei, Masoud; Bergadà Granyó, Josep Maria; Campo Sud, David del
When aimed to modify the downstream vortex shedding of a given bluff body, whether any road vehicle or wing profile, the use of Active Flow Control (AFC) appears to be an efficient technology. Among the different (AFC) methodologies the use of periodic forcing is ment to have better efficiency since it requires less energy to activate the shear layer, the reason behind this efficiency lies on the fact that periodic forcing interacts with the shear layer natural instabilites. In the present paper, one of the devices widely emloyed to generate pulsating flow, is carefully studied via 3D-CFD and using OpenFOAM. Initially the base flow is being determined and compared with previous experimental results, in a second step several internal dimensions of the fluidic actuator are being modified to characterize the output frequency and amplitude variations, among the conclusions obtained it is found that a given fluidic actuator is capable of generating several output frequencies and amplitudes when modifying some internal dimensions while maintaining a constant incoming flow Reynolds number.
Mon, 18 Sep 2017 12:43:44 GMThttp://hdl.handle.net/2117/1077322017-09-18T12:43:44ZBaghaei, MasoudBergadà Granyó, Josep MariaCampo Sud, David delWhen aimed to modify the downstream vortex shedding of a given bluff body, whether any road vehicle or wing profile, the use of Active Flow Control (AFC) appears to be an efficient technology. Among the different (AFC) methodologies the use of periodic forcing is ment to have better efficiency since it requires less energy to activate the shear layer, the reason behind this efficiency lies on the fact that periodic forcing interacts with the shear layer natural instabilites. In the present paper, one of the devices widely emloyed to generate pulsating flow, is carefully studied via 3D-CFD and using OpenFOAM. Initially the base flow is being determined and compared with previous experimental results, in a second step several internal dimensions of the fluidic actuator are being modified to characterize the output frequency and amplitude variations, among the conclusions obtained it is found that a given fluidic actuator is capable of generating several output frequencies and amplitudes when modifying some internal dimensions while maintaining a constant incoming flow Reynolds number.Square cylinder with passive flow controlhttp://hdl.handle.net/2117/107731
Square cylinder with passive flow control
An, Bo; Bergadà Granyó, Josep Maria; Mushyam, Aditya
In the present paper it is presented the flow around a 2D square cylinder which is located downstream of a splitter plate and at a certain distance of it. The fluid velocity below and above the splitter plate is different, several velocity ratios are considered, it is interesting to see that the downstream vortex shedding frequency and amplitude highly depends on the velocity ratio defined upstream. So far, the Reynolds numbers evaluated fall into the laminar unsteady regime, yet the interaction between the upstream mixing layer and the wake generate fully different downstream vortex shedding for different upstream velocity ratios, lift, drag and Strouhal numbers are as well highly dependent on the velocity ratios. In the present paper, the comparison between the results obtained via CFD finite volumes and Lattice Boltzmann Method are being presented. For these initial cases studied the agreement is very good.
Mon, 18 Sep 2017 12:33:10 GMThttp://hdl.handle.net/2117/1077312017-09-18T12:33:10ZAn, BoBergadà Granyó, Josep MariaMushyam, AdityaIn the present paper it is presented the flow around a 2D square cylinder which is located downstream of a splitter plate and at a certain distance of it. The fluid velocity below and above the splitter plate is different, several velocity ratios are considered, it is interesting to see that the downstream vortex shedding frequency and amplitude highly depends on the velocity ratio defined upstream. So far, the Reynolds numbers evaluated fall into the laminar unsteady regime, yet the interaction between the upstream mixing layer and the wake generate fully different downstream vortex shedding for different upstream velocity ratios, lift, drag and Strouhal numbers are as well highly dependent on the velocity ratios. In the present paper, the comparison between the results obtained via CFD finite volumes and Lattice Boltzmann Method are being presented. For these initial cases studied the agreement is very good.Thermo-fluid study of the upc race-track microtron cooling systemhttp://hdl.handle.net/2117/107493
Thermo-fluid study of the upc race-track microtron cooling system
Escaler Puigoriol, Francesc Xavier; Koubychine Merkulov, Youri Alexandrovich; Blasco Argente, Vicente Pablo; Romero Perea, Juan Antonio; Sánchez Díaz, Alexandre; Prieto, M.; Shvedunov, V.I.
The cooling system of the race-track microtron (RTM), which is under construction at the Universitat Politècnica de Catalunya (UPC), has been simulated by means of a computational fluid dynamics (CFD) software. The hydraulic and thermal performance of the system for various operation conditions has been studied. Firstly, the hydraulic model has been validated by comparison with experimental measurements at different flow rates. Then, the cooling fluid temperatures and the pressure losses of the system have been determined and the capacity of the current design to remove the generated heat at nominal power has been confirmed. Finally, the maximum and average wall temperatures and heat transfer coefficients inside the accelerating structure have been calculated. These results have allowed us to localize sections of the cooling system with a low convection due to detached flows where, therefore, a risk of zones of high temperatures exists. An optimization of the cooling circuit with the aim to reduce such high temperature zones has been proposed.
Thu, 07 Sep 2017 10:10:01 GMThttp://hdl.handle.net/2117/1074932017-09-07T10:10:01ZEscaler Puigoriol, Francesc XavierKoubychine Merkulov, Youri AlexandrovichBlasco Argente, Vicente PabloRomero Perea, Juan AntonioSánchez Díaz, AlexandrePrieto, M.Shvedunov, V.I.The cooling system of the race-track microtron (RTM), which is under construction at the Universitat Politècnica de Catalunya (UPC), has been simulated by means of a computational fluid dynamics (CFD) software. The hydraulic and thermal performance of the system for various operation conditions has been studied. Firstly, the hydraulic model has been validated by comparison with experimental measurements at different flow rates. Then, the cooling fluid temperatures and the pressure losses of the system have been determined and the capacity of the current design to remove the generated heat at nominal power has been confirmed. Finally, the maximum and average wall temperatures and heat transfer coefficients inside the accelerating structure have been calculated. These results have allowed us to localize sections of the cooling system with a low convection due to detached flows where, therefore, a risk of zones of high temperatures exists. An optimization of the cooling circuit with the aim to reduce such high temperature zones has been proposed.Thermo-fluid numerical simulation of the crotch absorbers’ cooling pinholes for alba storage ringhttp://hdl.handle.net/2117/107487
Thermo-fluid numerical simulation of the crotch absorbers’ cooling pinholes for alba storage ring
Escaler Puigoriol, Francesc Xavier; Arbó, Victor; Casas, Joan; Colldelram, Carles; Quispe, Marcos; Prieto Moline, María Montserrat
The ALBA Synchrotron Light Facility crotch absorbers, that remove the unused storage ring radiation, incorporate an internal cooling system composed by a number of parallel pinholes and by the corresponding stainless steel inner tubes inserted into each of them. Water flows in the resulting annular sections to evacuate the total heat power. Around each inner tube, a spiral wire is fixed along the whole length with a given pitch height in order to enhance the convection heat transfer. The influence of several design parameters on the absorber thermo-fluid behaviour has been evaluated by means of the CFD software ANSYS CFX¿. In particular, the wall heat transfer coefficients and the pressure losses through a single pinhole have been evaluated for a range of different flow rates and pitch heights. Moreover, some modifications of the end wall geometry have been simulated as well as the effect of reversing the flow direction inside the channels. Finally, the critical crotch absorber type 3 has also been simulated and the limiting pitch height-flow rate combinations have been found based on the available driving pressure of the cooling system.
Thu, 07 Sep 2017 09:25:56 GMThttp://hdl.handle.net/2117/1074872017-09-07T09:25:56ZEscaler Puigoriol, Francesc XavierArbó, VictorCasas, JoanColldelram, CarlesQuispe, MarcosPrieto Moline, María MontserratThe ALBA Synchrotron Light Facility crotch absorbers, that remove the unused storage ring radiation, incorporate an internal cooling system composed by a number of parallel pinholes and by the corresponding stainless steel inner tubes inserted into each of them. Water flows in the resulting annular sections to evacuate the total heat power. Around each inner tube, a spiral wire is fixed along the whole length with a given pitch height in order to enhance the convection heat transfer. The influence of several design parameters on the absorber thermo-fluid behaviour has been evaluated by means of the CFD software ANSYS CFX¿. In particular, the wall heat transfer coefficients and the pressure losses through a single pinhole have been evaluated for a range of different flow rates and pitch heights. Moreover, some modifications of the end wall geometry have been simulated as well as the effect of reversing the flow direction inside the channels. Finally, the critical crotch absorber type 3 has also been simulated and the limiting pitch height-flow rate combinations have been found based on the available driving pressure of the cooling system.Numerical simulation of the alba synchrotron light source cooling system response to pump start-up and shut-downhttp://hdl.handle.net/2117/107486
Numerical simulation of the alba synchrotron light source cooling system response to pump start-up and shut-down
Escaler Puigoriol, Francesc Xavier; Casas, Joan; Colldelram, Cales; Quispe, Marcos; Prieto Moline, María Montserrat
The ALBA Synchrotron Light Source cooling system is submitted to regular pump start-ups and shut-downs. Moreover, pumps can trip due to motor power failures. As a result, the piping system can be subjected to surges and pressure oscillations. The 1D thermo-fluid simulation software Flowmaster¿ has been used to predict these transient conditions taking into account the fluid compressibility, the pipe elasticity, the characteristic time response of the check valves and the pump/motors moments of inertia. During pump start-ups, significant pressure rises are detected that can be reduced by readjusting the PID controller parameters. Unexpected pump shutdowns do not appear to provoke significant water hammer conditions. However, pressure fluctuations are generated mainly in the same pumping line but also in the rest of the system due to the particular common return configuration. In all the cases the pressure regulation mechanisms acting on the pump rotating speeds serve to attenuate the consequences of these transients. Finally, the feasibility of the model to simulate the effect on the system response of trapped air inside the pipes has also been evaluated.
Thu, 07 Sep 2017 09:20:13 GMThttp://hdl.handle.net/2117/1074862017-09-07T09:20:13ZEscaler Puigoriol, Francesc XavierCasas, JoanColldelram, CalesQuispe, MarcosPrieto Moline, María MontserratThe ALBA Synchrotron Light Source cooling system is submitted to regular pump start-ups and shut-downs. Moreover, pumps can trip due to motor power failures. As a result, the piping system can be subjected to surges and pressure oscillations. The 1D thermo-fluid simulation software Flowmaster¿ has been used to predict these transient conditions taking into account the fluid compressibility, the pipe elasticity, the characteristic time response of the check valves and the pump/motors moments of inertia. During pump start-ups, significant pressure rises are detected that can be reduced by readjusting the PID controller parameters. Unexpected pump shutdowns do not appear to provoke significant water hammer conditions. However, pressure fluctuations are generated mainly in the same pumping line but also in the rest of the system due to the particular common return configuration. In all the cases the pressure regulation mechanisms acting on the pump rotating speeds serve to attenuate the consequences of these transients. Finally, the feasibility of the model to simulate the effect on the system response of trapped air inside the pipes has also been evaluated.